You can slip the pup up the straight track by having someone at the top to call/whistle him up. It's not good for any dog to be allowed to just run up and down the straight as this will jar up their legs and give them some bad habits.
Free galloping in a 100m yard is different, it's fine to do that (as long as it has deep soft sand at both ends)

I never use a lure when slipping dogs up the straight as they will work hard especially in pairs when you call them up (with a fluffy toy/squeeker/treat so you can easily catch them at the top of the straight).

Good luck with Spud :-)